The present invention relates to direct injection spark ignition engines and more particularly to, improving performance of such engines at high engine loads.
Conventional direct injection spark ignition engines typically have at least one combustion chamber having at least one air intake port for introducing air into the combustion chamber and a fuel injector port for directly injecting fuel into the combustion chamber. Fuel injection during compression stroke causes stratas of different air-fuel mixtures to be formed in the combustion chamber, the layer closest to the spark plug containing a stoichiometric or slightly rich of stoichiometry mixture, and with subsequent layers containing progressively leaner mixtures. Stratified mode is preferred for low engine loads and provides improved fuel economy.
At high engine loads, typically greater than 50% of full engine load, a homogeneous air-fuel mixture is provided in the combustion chamber by injecting fuel into the chamber during the intake stroke. At high loads, the air-fuel mixture is at or slightly rich of stoichiometry. When the air intake ports are open, the injected fuel spray is deformed by the incoming air stream and is blown to the intake port side. This prevents fuel droplets and vapor from penetrating across the cylinder and causes air-fuel mixture stratification. This condition can result in loss of power, and is particularly pronounced at high speed, high load conditions.
Various methods have been disclosed in the art of direct injection spark ignition engine design for improving engine performance at high load conditions by improving air-fuel mixture homogeneity. One method is described in Japan Patent Application No. 11,193,707 A, wherein improved air-fuel mixture homogeneity is achieved by providing a deflector at the bottom of the inner periphery of an intake valve of an intake air port deviated toward the side where a fuel injection valve is located. This causes the intake air to make a detour around the fuel injection valve, allowing the fuel to be injected at a wide angle and therefore improving air-fuel mixture homogeneity.
The inventors herein have recognized a disadvantage with this approach. Namely, the deflector is placed at the inner periphery of an air intake port in the vicinity of the intake valve, which has the problem of restricting the amount of air that can be injected into the combustion chamber, and can therefore cause the engine to be underpowered, most severely so at high speed, high engine loads.
An object of the present invention is to provide a method for improving performance of a vehicle equipped with a direct injection spark ignition engine.
The above object is achieved and disadvantages of prior approaches overcome by a direct injection, spark ignition internal combustion engine having a minimum of one combustion chamber formed in a cylinder block, and having a cylinder head attached to the block, the chamber comprising: a minimum of one air intake port formed in the cylinder head for introducing an air stream into the combustion chamber; a fuel injection port formed in the cylinder head for directly injecting a fuel spray into the combustion chamber; and an intake air deflector formed in the cylinder head between said air intake port and said fuel injection port, said deflector sized and positioned such as to reduce said air stream impinging on said fuel spray during an intake stroke of the engine.
In another aspect of the present invention the above object is achieved and disadvantages of prior approaches overcome by a method of forming a homogeneous air-fuel mixture in a combustion chamber of a direct injection spark ignition engine, the method comprising: inducting an air stream into the combustion chamber, said air stream impinging on a first side of an intake air deflector; and injecting a fuel spray into the combustion chamber, said fuel impinging on a second side of said intake air deflector.
In yet another aspect of the present invention, the above object is achieved and disadvantages of prior approaches overcome by a method of forming a homogeneous air-fuel mixture in a combustion chamber of a direct injection, spark ignition internal combustion engine, the method comprising: inducting an air stream through an air intake port housed in a lower plateau protruding into the combustion chamber, said lower plateau formed in a cylinder head; and simultaneously injecting a fuel spray through a fuel injection port housed in an upper plateau, said upper plateau formed in said cylinder head and separated from said first plateau by a step of about 1-25 millimeters in height.
An advantage of the above aspects of the invention is that by preventing the intake air from deflecting the fuel spray to the intake side of the combustion chamber during the intake stroke of the engine, fuel droplets and vapor are allowed to be better distributed throughout the combustion chamber, and thus better air-fuel mixture homogenization is achieved. Since the deflector is formed in the cylinder head between the fuel injector port and the air intake port(s), and not inside the air intake port as in the prior art invention, the flow of intake air is not restricted, and thus higher output torque and better engine performance at high engine loads is achieved.
Other objects, features and advantages of the present invention will be readily appreciated by the reader of this specification.